Drill bit with wear resistant material on blade



Jan. 3 1, 1967 E. s. PENNEBAKER, JR 3,301,339

DRILL BIT WITH WEAR RESISTANT MATERIAL ON BLADE Filed June 19, 1964 5 Sheets-Sheet l BORE-HOLE II I FIG. I.

CONTACT POINT.

DRILL COLLARS |2 REAMING' EDGE OF a INVENTOR.

EUGENE s. PENNEBAKER JR.,

I ATTORN Jan. 31,1967 E. s. PENNEBAKER, JR 3,301,339

DRILL BIT WITH- WEAR RESISTANT MATERIAL ON BLADE Filed June 19, 1964 5 Sheets-Sheet 2 FIG. 4.

INVENTOR.

BY azwa ATTOR v.

EUGENE S. PENNEB AKER,JR.,

1967 E. s. PENNEBAKER, JR v 3,301,339

DRILL BIT WITH WEAR RESISTANT MATERIAL ON BLADE .Filed June.l9. 1964' I 5 heets-Sheet s INCREASED HARDNESS FROM CENTER INVENTOR. EUGENE S. PENNEBAKER, JR,,

United States Patent 3,301,339 DRILL BIT WITH WEAR RESISTANT MATERIAL 0N BLADE Eugene S. Pennebaker, Jr., Corpus Christi, Tex., assignor, by mesne assignments, to Esso Production Research Company, Houston, Tex., a corporation of Delaware Filed June 19, 1964, Ser. No. 376,439 9 Claims. (Cl. 175387) The present invention is directed to a drill bit which has improved stability performance in drilling vertical wells. More particularly, the invention is concerned with an improved drill bit of the drag type. In its more specific aspects, the invention is concerned with a drag type bit that drills a straight, fast hole and has improved penetration performance.

The present invention may be briefly described as a drill bit adapted to be attached to a hollow drill string. The drill bit comprises a body member having -a plurality of spaced-apart blades attached thereto. Each of the blades has a length no greater than the distance from the center of the body member to the outer edge of the blades and the blades have a ratio of length to thickness within the range from about 3:1 to about 4:1. Theblades extend inwardly toward, but terminate short of the center of the body member to provide a space at the center of the body member. The leading face of each of the blades is covered with abrasive material which extends over the leading face or substantially covers the leading face. The abrasive material is of progressively increasing hardness orprogressively increasing thickness such that it provides progressively increasing wear resistance to each of thebladesfrom the inner to the outer edge of the blades. A core breaker extends from the body member into the space at the center of the body member, the core breaker having a surface on its free end defining means for deflecting a core broken by the core breaker.

Fluid passageways are defined by the body member and terminate in nozzles adapted to direct fluid to a point ahead of the blades.

The blades have a length in the range from about 2 to about 3 inches measured from the end of the bit body for a 6 A-inch gauge bit and proportionately the same length for other size bits. For example, the blade length for an 8%-inch gauge bit may be within the range from I about 2% inches to about 4 inches.

The bits of the present invention may be used to drill boreholes from about 4 inches to about 9 inches in diameter, but larger holes may also be drilled with the improved bit. The core formed at the center of the bit is determined by the size of the space at the center of the bit and the core may be from about inch to about 1 inch in diameter. Hence, the distance from the inner edge of each blade to the center of the bit is suitably within the range from about 1 inch to about inch.

The core breaker should be as short as possible to cut a core even when the blades may become worn. A suitable length measured from the bit body for the core breaker is from about /2 inch to about inch with the angle of the deflecting means being within the range from about 20 to about 45 with respect to the plane atthe identical.

FIG. 5 is an isometric view of a preferred embodiment of the present invention.

It is desirable to make a bit drill fast and straight. In drilling with a bit, the penetration rate is proportional to the unit loading on bottom with other factors being equal. Thus for a given bit weight, the sharper the bit the faster the bit drills. As the bit becomes dull and begins to present an increasingly greater bearing area on bottom, bit weight must be increased to maintain the same unit loading. Thus, if the bit blade thickness is large, the bearing area on well bottom increases rapidly as the blade wears. Available drill collar weight thus becomes inadequate to maintain the same unit loading, and penetration rate slows. As drill collar weight is added to increase bit weight, the lower part of the drill collar string begins to bow. The bit is thus deflected at a slight angle to the borehole by an amount proportional to the severity of the bow. As an example: in a 7% -inch hole drilling with 6%- inch drill collars, if suflicient weight is applied to cause the drill collars to touch the side of the hole 30 feet above the bit, the axis of the bit will be aimed at such an angle to the hole that it will deflect the hole about one inch in 30 feet assuming no sidewise cutting action of the bit. Thus, deflecting action becomes cumulative, that is, the angle would not remain constant but would gradually increase. It is therefore important to consider the factors that keep a hole vertical at the same time penetration rate is considered.

In drilling a straight hole, the only force available to make a bit on the end of a flexible drill string drill a truly vertical hole is gravity, as shown in FIG. 1. Thus, in FIG. 1, in a borehole 11 drilled from the earths surface with a drill string 12 extending thereto, the weight of the drill collar W between the point of contact P and the bottom of the bit creates a force F acting downwardly by gravity. A horizontal force F results. The ability of the reaming edge of the bit to cut in the direction of the resultant horizontal force will then determine whether the direction of the borehole gradually returns to the vertical along directionD and continues along the same angle of deviation from the vertical along direction B or gradually builds up more along direction A. The ability of the bit to cut sideways therefore depends on the sharpness of the reaming edge and/or the length of the reaming blade. Thus, if for any reason the bit deviates from the vertical, the bit must drill sideways to return the hole to the vertical. Considering the bending action of the drill string as discussed before, it is readily seen that the bit must be capable of cutting laterally or it would not be possible to drill a vertical hole using the relatively limber or flexible drill collar system for weight as is currently done.

The problems of drilling a vertical hole are solved in accordance with the present invention by providing the apparatus which will be described relative to FIGS. 2 to 5.

Referring now to FIGS.v 2 to .4 in which identical numerals will designate identical parts, numeral 13 designates a body member which is adapted to be attached to a drill string, such as 12 of FIG. 1, in drilling a borehole I l. The body member has attached to it a plurality of blades, such as at least three blades designated by the numerals 14, 17 and 19. In the embodiment of FIG. 2, the blades 14, 17 and 19 are different but ordinarily in a drill bit these three blades are substantially The bit blade 14 tapers outwardly from a point short of the center of the body member 13 and is FIG. 4 is an edge view 'of one of the blades of FIG. 2; I

and

to provide increasing ab-rasiveness to the blade 14.

provided 'with plates 15 of abrasive material such as tungsten carbide, which substantially cover the leading face of the blade 14. The outer plate 15 covering the blade 14 may suitably be impregnated with diamonds 16 It will be noted that the outer plate 15 is impregnated with diamonds; whereas, the next plate 15 is not impregnated with diamonds and the two inner plates '15 are of decreasing thickness. Thus, the plates 15 provide progressively increasing wear resistance to the blade 14 extending outwardly from the inner to the outer edge of the blade 14.

This is illustrated also by blade 17 which is provided with plates 18 of tungsten carbide of progressively increasing thickness extending from the inner edge to the outer edge.

Blade 18 is provided with plates 20 of tungsten carbide of progressively increasing hardness extending from the inner edge of the outer edge. Also, the blade 19 is provided with formed inserters 21 of tungsten carbide or other abrasive material of progressively increasing size or hardness from the inner to the outer edge. These inserts may be cylindrical or other shapes, such as the oblong shape 22.

It will be noted that the blade '14 has a taper and differs in shape from blades 17 and 19.

The body member 16 is provided with water courses terminating in nozzles 23 which are adapted to discharge drilling fluid from the hollow drill string ahead of each of the blades 14, 17 and 19.

Each of the blades 14, 17 and 19 (only one of which is illustrated in FIG. 3) is provided with a pilot blade. Taking blade 14, for example, this blade is provided on its free end with a pilot blade 24 which projects ahead of the blade 14. The pilot blade 24 is also provided with a plate 25 of abrasive material, such as tungsten carbide.

The three blades 14, -17 and 19 provide a space at the center of the body member 13 in which is arranged a core breaker 26 defining a surface 27 which serves as a coredeflecting means.

The several blades described with respect to FIGS. 2 to 4 are made of tough, high alloy steel, preferably forged steel, and are attached to the body member by welding after machining and attachment of the tungsten carbide plates. The blades are relatively thin and have a ratio of blade length to thickness preferably in the range of about 3:1 to about 4:1 and taper toward the cutting edge, as shown more clearly in FIG. 4.

FIG. 4 shows another arrangement of a blade designated as blade 28 provided with a taper 29. The blade 28 is provided with plates 30 of abrasive material, such as tungsten carbide, and the edge 29 may suitably be provided with diamond-impregnated tungsten carbide inserts 31 to provent excessive gauge wear. The exposed diamonds also provide lateral cutting action for the maintenance of a vertical hole.

Referring now to FIG. 5, a drill bit such as 40 is provided with a threaded pin 41 for attachment to a drill string such as .12. A body member 42 has attached thereto by welds 43 three spaced-apart blades 44. The blades 44 each is provided with a pilot blade 45 and the leading face of each blade, including the pilot blade, is substantially covered with plates 46 of abrasive material, such as tungsten carbide, which provides progressively increasing wear resistance from the inner edge 47 to the outer edge 48 of the blades '44. The body member 42 is provided with a plurality of nozzles 23 which communicate with the interior of the body member 42 and with the hollow drill string for circulation of drilling fluid down the drill string and up the annulus between the drill string and the wall of the well. The nozzles 23 are arranged to direct fluid ahead of the leading faces of the blades 44. The space 49 at the center of the drill bit '40 is provided with a core breaker 50 defining a deflecting surface 51 for deflecting the core broken by the core breaker 50.

In drilling with the drill bit of the present invention, the drill bit is attached to a hollow drill string and is rotated by the usual rotating means at the wellhead. As the bit penetrates by scraping action, cuttings generated by this scraping action are broken up and flushed to the surface by drilling fluid pumped through jet nozzles aimed at and slightly adhead of each blade. Since the scraping action is small at the center of the hole where the blades approach each other, it is desirable that the material in the center of the hole he removed and this is done by the core breaker, such as 50, and the core-deflecting means 51.

The bit in accordance with the present invention allows rapid penetration of formations and drills a substantially vertical hole which heretofore was difficult to achieve, particularly with drag type rbits. Thus, the bit blades are of a proper length such that they remain sharp but do not break off due to lack of strength. By employing a plurality of blades, such as at least three, smooth drilling action is achieved. While heretofore 3-way drag bits drilled slowly and deviated rapidly, the present invention, by virtue of the particular elements and arrangernent thereof, drills rapidly and straight.

While the abrasive material has been illustrated by sintered tungsten carbide and diamonds, other abrasive mate-rial such as, but not limited to various other carbides and special Wear-resistance alloys may be employed. Sintered tungsten carbide is preferred.

The present invention has been used successfully in drilling substantial footage of vertical holes at drilling rates greater than that achieved with comparable commercial bits. The present invention is therefore quite important and useful.

The nature and objects of the present invention having been completely described and illustrated and the best mode and embodiment thereof contemplated set forth, what I wish to claim as new and useful and secure by Letters Patent is:

1. A drill bit adapted to be attached to a hollow drill string which comprises a body member, a plurality of spaced-apart blades attached to said body member, each of said blades having a length no greater than the distance from the center of the body member to the outer edge of said blades, said blades extending inwardly toward but terminating short of the center of said body member to provide a space at the center of said body member, abrasive material of progressively increasing hardness on the leading face of each of said blades, said abrasive material providing progressively increasing wear resistance to each of said blades from the inner to the outer edge of each of said blades, a core breaker extending from said body member into said space and having a surface on its free end defining means for deflecting a core broken by said core breaker, and fluid passageways defined by said body member terminating in nozzles adapted to direct fluid to a point ahead of each of said blades.

2. A drill bit adapted to be attached to a hollow drill string which comprises a body member, at least three spaced-apart blades attached to said body member, each of said blades having a length no greater than the distance from the center of the body member to the outer edge of said blades and having a ratio of length to thickness within the range from about 3 to about 1 to about 4 to about 1, said blades extending inwardly toward but terminating short of the center of said body member to provide a space at the center of said body member, abrasive material of progressively increasing hardness on the leading face of each of said blades, said abrasive material providing progressively increasing wear resistance to each of said blades from the inner to the outer edge of each of said blades, a core breaker extending from said body member into said space and having a surface on its free end defining means for deflecting a core broken by said core breaker, and fluid passageways defined by said body member terminating in nozzles adapted to direct fluid to a point ahead of each of said blades.

3. A drill bit adapted to be attached to a hollow drill string which comprises a body member, at least three paced-apart blades attached to said body member, each of said blades having a length no greater than the distance from the center of the body member to the outer edge of said blades and having a ratio of length to thickness within the range from about 3 to about 1 to about 4 to about 1, said blades extending inwardly toward but terminating short of the center of said body member to provide a space .at the center of said body member, a pilot blade projecting from the free end of each of said blades, abrasive material of progressively increasing hardness on the leading face of each of said blades including said pilot blades, said abrasive material providing progressively increasing wear resistance to each of said blades from the inner to the outer edge of each of said blades, a core breaker extending from said body member into said space and having a surface on its free end defining means for deflecting a core broken by said core breaker, and fluid passageways defined by said body member terminating in nozzles adapted to direct fluid to a point ahead of each of said blades.

4. A drill bit adapted tobe attached to a hollow drill string which comprises a body member, at least three spaced-apart blades attached to said body member, each of said blades having a length no greater than the distance from the center of the body member to the outer edge of said blades, said blades extending inwardly toward but terminating short of the center of said body member to provide .a space at the center of said body member, abrasive material of progressively increasing hardness on the leading fiace of each of said blades, the free end and edge of each of said :blades also being provided with formed inserts of abrasive material of progressively increasing hardness, said abrasive material providing progressively increasing wear resistance to each of said blades from the inner to the outer edge of each of said blades, a core breaker extending from said body member into said space and having a surface on its free end defining means for deflecting a core broken by said core breaker, and fluid passageways defined by said body member terminating in nozzles adapted to direct fluid to a point ahead of each of said blades.

5. A drill bit adapted to be attached, to :a hollow drill string which comprises a :body member, at least three spaced-apart blades attached to said body member, each of said blades having a length no greater than the distance from the center of the body member to the outer edge of said blades and having a ratio of length to thickness within the range from about 3 to about 1 to about 4 to about 1, said blades extending inwardly toward but terminating short of the center of said body member to provide a space at the center of said body member, a pilot blade projecting from the free end of each of said blades, sintered tungsten carbide substantially covering the leading face of each of said blades including said pilot blades, said tungsten carbide providing progressively increasing wear resistance to each of said blades including said pilot blades from the inner to the outer edge of each of said blades, the free end of each of said blades including said pilot blades also being provided with formed tungsten carbide inserts, a core breaker extending from said body member into said space and having a surface on its free end defining means for deflecting a core broken by said core breaker, and fluid passageways defined by said body member terminating in nozzles adapted to direct fluid to a point ahead of each of said blades.

6. A drill bit in accordance with claim 5 in which said inserts also provide increasing Wear resistance from the inner to the outer edge of said pilot blades.

7. A drill bit adapted to be attached to a hollow drill string which comprises a :body member, -a plurality of spaced apart blades attached to said body member, each of said blades having a length no greater than the distance from the center of the body member to the outer edge of said blades, abrasive material of progressively increasing hardness on the leading face of each of said blades, said abrasive material providing progressively increasing wear resistance to each of said blades from the inner to the outer edge of each of said blades, and fluid passageways defined by said body member terminating in nozzles adapted to direct fluid to a point ahead of each of said blades.

8. A drill bit in accordance with claim 7 in which the blades extend inwardly to ward but terminate short of the center of the body member to provide :a space at the center of the body member and in which core breaking means are provided in said space.

9. A drill bit in accordance with claim 7 in which a pilot blade projects from the free end of each of said blades having abrasive material of progressively increasing hardness on the leading face of said pilot blade, said abrasive material on said pilot blade providing progressively increasing wear resistance from the inner to the outer edge of said pilot blade.

References Cited by the Examiner UNITED STATES PATENTS 2,740,612 4/1956 Phipps -404 3,106,973 10/1963 Christensen 175410 3,127,945 4/1964 Bridwell et al 175-410 3,140,748 7/1964 Engle et a1 175410 3,145,790 8/1964 Bridwell et al. 175-409 3,199,617 8/ 1965 White 175404 FOREIGN PATENTS 900,099 7/ 1962 England.

CHARLES E. OCONNELL, Primary Examiner.

JAM S LEPP NK, xaminer. 

7. A DRILL BIT ADAPTED TO BE ATTACHED TO A HOLLOW DRILL STRING WHICH COMPRISES A BODY MEMBER, A PLURALITY OF SPACED APART BLADES ATTACHED TO SAID BODY MEMBER, EACH OF SAID BLADES HAVING A LENGTH NO GREATER THAN THE DISTANCE FROM THE CENTER OF THE BODY MEMBER TO THE OUTER EDGE OF SAID BLADES, ABRASIVE MATERIAL OF PROGRESSIVELY INCREASING HARDNESS ON THE LEADING FACE OF EACH OF SAID BLADES, SAID ABRASIVE MATERIAL PROVIDING PROGRESSIVELY INCREASING WEAR RESISTANCE TO EACH OF SAID BLADES FROM THE INNER TO THE OUTER EDGE OF EACH OF SAID BLADES, AND FLUID PASSAGEWAYS DEFINED BY SAID BODY MEMBER TERMINATING IN NOZZLES ADAPTED TO DIRECT FLUID TO A POINT AHEAD OF EACH OF SAID BLADES. 